// This optional code is used to register a service worker.
// register() is not called by default.

// This lets the app load faster on subsequent visits in production, and gives
// it offline capabilities. However, it also means that developers (and users)
// will only see deployed updates on subsequent visits to a pages, after all the
// existing tabs open on the pages have been closed, since previously cached
// resources are updated in the background.

// To learn more about the benefits of this model and instructions on how to
// opt-in, read https://bit.ly/CRA-PWA

const isLocalhost = Boolean(
    window.location.hostname === 'localhost' ||
    // [::1] is the IPv6 localhost address.
    window.location.hostname === '[::1]' ||
    // 127.0.0.1/8 is considered localhost for IPv4.
    window.location.hostname.match(
        /^127(?:\.(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)){3}$/,
    ),
)

type Config = {
    onSuccess?: (registration: ServiceWorkerRegistration) => void;
    onUpdate?: (registration: ServiceWorkerRegistration) => void;
};

export function register(config?: Config) {
    if (process.env.NODE_ENV === 'production' && 'serviceWorker' in navigator) {
        // The URL constructor is available in all browsers that support SW.
        const publicUrl = new URL(
            (process as { env: { [key: string]: string } }).env.PUBLIC_URL,
            window.location.href,
        )
        if (publicUrl.origin !== window.location.origin) {
            // Our service worker won't work if PUBLIC_URL is on a different origin
            // from what our pages is served on. This might happen if a CDN is used to
            // serve assets; see https://github.com/facebook/create-react-app/issues/2374
            return
        }

        window.addEventListener('load', () => {
            const swUrl = `${process.env.PUBLIC_URL}/service-worker.js`

            if (isLocalhost) {
                // This is running on localhost. Let's check if a service worker still exists or not.
                checkValidServiceWorker(swUrl, config)

                // Add some additional logging to localhost, pointing developers to the
                // service worker/PWA documentation.
                navigator.serviceWorker.ready.then(() => {
                    console.log(
                        'This web app is being served cache-first by a service ' +
                        'worker. To learn more, visit https://bit.ly/CRA-PWA',
                    )
                })
            }
            else {
                // Is not localhost. Just register service worker
                registerValidSW(swUrl, config)
            }
        })
    }
}

function registerValidSW(swUrl: string, config?: Config) {
    navigator.serviceWorker
             .register(swUrl)
             .then(registration => {
                 registration.onupdatefound = () => {
                     const installingWorker = registration.installing
                     if (installingWorker == null) {
                         return
                     }
                     installingWorker.onstatechange = () => {
                         if (installingWorker.state === 'installed') {
                             if (navigator.serviceWorker.controller) {
                                 // At this point, the updated precached content has been fetched,
                                 // but the previous service worker will still serve the older
                                 // content until all client tabs are closed.
                                 console.log(
                                     'New content is available and will be used when all ' +
                                     'tabs for this pages are closed. See https://bit.ly/CRA-PWA.',
                                 )

                                 // Execute callback
                                 if (config && config.onUpdate) {
                                     config.onUpdate(registration)
                                 }
                             }
                             else {
                                 // At this point, everything has been precached.
                                 // It's the perfect time to display a
                                 // "Content is cached for offline use." message.
                                 console.log('Content is cached for offline use.')

                                 // Execute callback
                                 if (config && config.onSuccess) {
                                     config.onSuccess(registration)
                                 }
                             }
                         }
                     }
                 }
             })
             .catch(error => {
                 console.error('Error during service worker registration:', error)
             })
}

function checkValidServiceWorker(swUrl: string, config?: Config) {
    // Check if the service worker can be found. If it can't reload the pages.
    fetch(swUrl)
        .then(response => {
            // Ensure service worker exists, and that we really are getting a JS file.
            const contentType = response.headers.get('content-type')
            if (
                response.status === 404 ||
                (contentType != null && contentType.indexOf('javascript') === -1)
            ) {
                // No service worker found. Probably a different app. Reload the pages.
                navigator.serviceWorker.ready.then(registration => {
                    registration.unregister().then(() => {
                        window.location.reload()
                    })
                })
            }
            else {
                // Service worker found. Proceed as normal.
                registerValidSW(swUrl, config)
            }
        })
        .catch(() => {
            console.log(
                'No internet connection found. App is running in offline mode.',
            )
        })
}

export function unregister() {
    if ('serviceWorker' in navigator) {
        navigator.serviceWorker.ready.then(registration => {
            registration.unregister()
        })
    }
}
